Animal fats such as pork fat, chicken fat, lamb tallow, and beef tallow are widely used for making animal food products due to their nutritional values to animals and their economic value to food manufacturers. The raw materials used to produce these fats usually contain animal offal or viscera. However, the fats derived from these materials (in particular, inedible fats) usually have strong and offensive odors (such as odors of blood, footy, ammonia, and unfresh) and an undesirable, dark appearance. Furthermore, these fats are susceptible to microbial contamination.
It is thought that the free fatty acids present in animal fats, and in particular, inedible animal fats, are responsible for offensive odors. A known physical refining process for removing free fatty acids from fat/oil sources involves injecting steam into heated fat/oil under vacuum. The thermal energy and polar environment provided by the steam releases free fatty acids within the fat/oil material. These in turn evaporate under vacuum, diminishing the odor of the fats. This process is more commonly used for processing vegetable oils rather than animal fats. A known chemical refining process for removing free fatty acids from fat/oil sources involves neutralizing free fatty acids in fat/oil using an excess of caustic soda (sodium hydroxide), removing the soap stock, heating to a temperatures of up to about 88° C. (190° F.), separating saponified soap stocks through water washing, centrifuging, and drying. However, excessive saponification imparts an undesirable soapy odor to the fat/oil source and reduces process yield. Recent product development and market competition have driven pet food manufacturers to use higher grade animal fats from premium sources. However, the use of these higher grade materials is constrained by costs and sourcing. Furthermore, even these higher grade materials are still susceptible to microbial contamination.
It would be desirable to provide an improved method of processing animal fat, particularly inedible animal fat, which effectively diminishes the odor associated with fatty acids present in the fat, which imparts good aromas to the finished material, and which reduces or eliminates the risk of microbial contamination to comply with microbial safety standards, without diminishing the palatability of the fat. The method should be feasible both technologically and economically.